A conventional outboard marine engine of this type is supported by an engine bracket, which is supported pivotably on a tilt tube (a through tube). The tilt tube extends along a horizontal tilt axis, around which the outboard marine engine can tilt. The tilt tube extends through a clamp bracket, which is fixed to a boat hull. The outboard marine engine can turn around a steering axis, which is roughly perpendicular to the engine bracket, to steer the boat. In general, the boat can be steered either hydraulically with a hydraulic cylinder or mechanically with push-pull cables by turning the steering handle.
A boat fitted with an outboard marine engine of relatively low horsepower can be steered mechanically with push-pull cables. A boat fitted with an outboard marine engine of high horsepower can be steered with a hydraulic cylinder, which slides along a horizontal piston rod. Both ends of the piston rod are supported by a pair of arms, which is supported by both ends of a horizontal tilt tube.
For example, Japanese Examined Patent Publication No. H3-33559 (pages 1–6 and FIG. 2) discloses an outboard marine engine, which is connected to a hydraulic cylinder by a steering lever. The hydraulic cylinder can slide along a piston rod, both ends of which are supported by a pair of arms. The arms are supported pivotably by both ends of a tilt tube.
There are various types of clamp brackets which can be fitted on boat hulls. The clamp brackets are classified mainly as detachable brackets suitable for boats and fixed brackets, which can be screwed in advance to boat hulls.
Each of the detachable brackets includes a hook, which extends downward and is fitted with a clamp.
When an outboard marine engine which can be turned by a hydraulic cylinder tilts upward up to 75 degrees, the parts supporting the cylinder may interfere with the clamp bracket supporting the engine, depending on the bracket type. Therefore, there are demands for a hydraulic cylinder type steering apparatus which can be fitted to any type of clamp bracket, and which can tilt up to the maximum of 75 degrees.
The hydraulic cylinder can slide along a piston rod, which is supported by a pair of arms. The arms are supported by both ends of a tilt tube, which extends along the tilt axis. Both ends of the tilt tube have threads cut outside them. Different tilt tubes may have end threads of different sizes.
When the hydraulic cylinder slides along the piston rod, the steering angles on both sides may differ depending on the initial position of the cylinder, and/or on how the cylinder is connected to a steering lever, which connects it to the outboard marine engine. This makes it difficult to steer the boat to a maximum of 35 degrees equally on each side.